sRGB back to Adobe RGB

Hi all!
I have shot some jpeg's with 20D set to sRGB can I change them to Adobe RGB? or is it too late.
Thanks.
Tony.

I think it's too late. FWIW, if you shoot in RAW, as you convert to JPEG you can select the color space and if you saved the RAW shots, you can reconvert to JPEG with different color spaces.

Thanks TEE WHY.
I did shoot 1 of the pics in raw, so that one is ok.
Thanks again.
Tony.

Why would you want to? Unless they MUST be in Adobe RGB leave them as-is. Use "convert to profile" (NOT assign). Plenty of pros shoot sRgb JPG and have great results. The conversion is very slightly destructive but not so much a human eye could probably notice it, do it a dozen times then maybe, but only maybe. The loss is probably more theoretical, i've never tried it.

tim wrote in post #3346809
Why would you want to? Unless they MUST be in Adobe RGB leave them as-is. Use "convert to profile" (NOT assign). Plenty of pros shoot sRgb JPG and have great results. The conversion is very slightly destructive but not so much a human eye could probably notice it, do it a dozen times then maybe, but only maybe. The loss is probably more theoretical, i've never tried it.

They are photos I shot in sRGB quite a while ago and the people they are going to want them in adobe RGB. Thanks Tim.
Regards Tony.

Technically, you can do the conversion (in order to satisfy those people) but practically you don't gain anything from it since the computer can't restore the colors that were discarded by the compression to sRGB.

I think you're better off explaining that the pictures are in sRGB. 8 bit sRGB to 8 bit Adobe RGB is a destructive transformation for sure, and may just lead to some posterisation as you have the same 0-255 R, G and B space representing a wider range of colours.

In other words, converting 8 bit sRGB to 8 bit Adobe RGB reduces the number of possible colours in the image, as you have the same number of values spread across a larger colour space, which means you can represent fewer discrete colours from the original image. Some of the possible Adobe RGB values can't appear in the resulting image - as they represent colours outside the sRGB gamut - anyone plotting a gamut chart of your picture will realise this.

The only way you'll get colours in the image that are outside the sRGB gamut is if you're post-processing them into the image - if colours in the Adobe RGB gamut but outside the sRGB gamut were present in camera, the camera will have moved them inside the sRGB gamut.

Finally, any colour managed workflow should deal with the image being sRGB.


I can appreciate that various organisations have standards for what they want - but I'm always uneasy about turning images into something that they're not. If they want 8 megapixel Adobe RGB and you have 6 megapixel sRGB, I'd rather tell them the truth (particularly if the shot is older). They may well get better results working with your image as it is - though if they want to resample it and/or convert to Adobe RGB (which, as I said, I can only think will lead to worse results than leaving well alone), they can at least do so in a way that's aware of their eventual use for the image.

If you make these sort of changes yourself, particularly if you do it in a way that conflicts with their processes, the end results will be worse than if you supplied what you had.


If you had a RAW file, you could (and should) have reprocessed it to meet the requirement. If all you have is an sRGB JPEG, why not explain that to the organisation? This is one reason why I always shoot RAW - I can appreciate that there are some scenarios where camera JPEGs make sense, even on RAW capable cameras.


I recently licensed two pictures from a photographer; my request was for 16 bit TIFFs with embedded profiles in the widest gamut colour space and highest resolution that he had. What I got were 8 bit unsharpened sRGB TIFFs - which was fine for me. That was all the photographer's relatively modest film scanner could manage, and as one of the two images was very old, I doubt there was much more to be had from what I suspect was an ageing negative.

As the images are going to be used in a process that has a gamut no wider than sRGB, the only reason I asked for 16 bit and wider gamut spaces was to give me a bit more post-processing latitude (I sought and was granted permission to post-process the original images to fit my needs).


I'm sure I'm not alone in asking for 16 bit, wide gamut working spaces and so on - but being happy when I'm given what the photographer actually has, rather than an artificial attempt to turn the file into something it isn't.

David

never understood in poor words the gain to use adobeRGB

Adobe RGB has a wider gamut than sRGB - if I remember rightly, particularly in the greens and blues. Many inkjet printers, particularly at the higher end, share this wider gamut - so by using Adobe RGB, you can get these shades that you'd miss out on if using sRGB.

The disadvantage is that without proper colour management, Adobe RGB images look wrong - for the web, you should use sRGB, for example.


If you don't understand colour management, your best bet is to stick with sRGB.

David

DavidW wrote in post #3347454
Adobe RGB has a wider gamut than sRGB - if I remember rightly, particularly in the greens and blues. Many inkjet printers, particularly at the higher end, share this wider gamut - so by using Adobe RGB, you can get these shades that you'd miss out on if using sRGB.

The disadvantage is that without proper colour management, Adobe RGB images look wrong - for the web, you should use sRGB, for example.

If you don't understand colour management, your best bet is to stick with sRGB.


David

Thats what I would normally advise.
I think 'Tim' once told me this, so it must indeed be wise words

DavidW wrote in post #3347286
The only way you'll get colours in the image that are outside the sRGB gamut is if you're post-processing them into the image - if colours in the Adobe RGB gamut but outside the sRGB gamut were present in camera, the camera will have moved them inside the sRGB gamut.

I think Perceptual rendering intent will give you colors that are outside sRGB Gamut, since the entire image is 'remapped'. It doesn't mean that they represent the actual (real life) colors though (In fact: Likely not)...

René Damkot wrote in post #3347495
I think Perceptual rendering intent will give you colors that are outside sRGB Gamut, since the entire image is 'remapped'. It doesn't mean that they represent the actual (real life) colors though (In fact: Likely not)...

Perceptual will remap all the colours. I'm honestly not sure whether that would map anything to colours outside sRGB gamut; normally perceptual is used to compress the colours in a wider gamut space into a narrower colour space. sRGB to Adobe RGB using perceptual is 'backwards'; it's possible that you'll finish up with false colours that are sometimes outside the sRGB gamut. I'm not enough of a colour management guru to be sure.

If I was going to convert sRGB to Adobe RGB, I'd use relative colorimetric - but I still maintain that it's a bad idea.

David

René Damkot wrote in post #3347495
I think Perceptual rendering intent will give you colors that are outside sRGB Gamut, since the entire image is 'remapped'. It doesn't mean that they represent the actual (real life) colors though (In fact: Likely not)...

Remapping colors going from sRGB to Adobe RGB shouldn't be a problem because all the sRGB colors should be present in the Adobe RGB color space. It's when you go from a larger to a smaller gamut where perceptual rendering can becomes a "problem" due to possible color shifts.

sRGB is a smaller color space than aRGB, but that doesn't mean there isn't colors outside the gamut of aRGB.

Perceptual rendering intent will try and keep the overall colors the same and move the destination "out of gamut" colors to the closest color match to source.

Relative Colorimetric rendering intent will match the "white" and clip the destination "out of gamut" colors.

So I believe the rendering intent you choose should be based on the color content/range of you picture i.e., try it both ways and go with what suits you!

gparvan wrote in post #3349942
sRGB is a smaller color space than aRGB, but that doesn't mean there isn't colors outside the gamut of aRGB.

Perceptual rendering intent will try and keep the overall colors the same and move the destination "out of gamut" colors to the closest color match to source.

Relative Colorimetric rendering intent will match the "white" and clip the destination "out of gamut" colors.

So I believe the rendering intent you choose should be based on the color content/range of you picture i.e., try it both ways and go with what suits you!

Then can you point out what those colors are that sRGB has that's not in the Adobe color space? I'm looking at both color spaces simultaneously from all angles and I can't find any sRGB color that goes outside the color gamut of the Adobe RGB color space. The Adobe RGB color space completely engulf the sRGB color space as far as I can see.